Novelmethod is proposed for spectrophotometric determination of chloramine- B (CAB) in various environmentalwater samples. Themethod is based on the reduction of CAB by electrophilic coupling reagent, 3-methyl-2- benzothiozoline hydrazone hydrochloride hydrate (MBTH) and subsequent coupling ofMBTH with trimipramine maleate (TPM) in acidic mediumto formblue coloured product having ï¬max at 630nm. The colour was stable up to 24h and obeyed BeerÂs Law. The optimum reaction conditions and other important analytical parameters are established to enhance the sensitivity of the proposed method. Interference due to various non-target ions is also investigated. The proposed methods can be applied to the analysis of CAB in different water samples. The performance of proposed method can be evaluated in terms of recovery tests by standard addition method.